1. Field of the Invention
The present invention relates generally to controlling the clock signal distributed to a device by a Direct Memory Access controller along a bus.
2. Description of the Related Art
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Direct Memory Access (“DMA”) controllers are widely used in modern electronic devices. The DMA controller may be used to transfer data in an electronic device without burdening the central processing unit (“CPU”). A CPU typically requires a list of commands, or instructions, to operate. These instructions are often grouped together as a program. Programs are typically stored in long term storage devices, such as a hard disk drive or non-volatile memory. Accessing these long term storage devices may require a certain amount of time, during which time the CPU must idly wait.
The use of a DMA controller can reduce the time a CPU must remain idle. Typically, the CPU hands off the fetching of the list of instructions that are grouped together as a program that will be needed in the immediate future to a DMA controller. The CPU may then be free to execute previously fetched instructions while the DMA fetches the program for the CPU. DMA controllers usually transfer data between a location in memory and an I/O device or between an I/O device and a location in memory. DMA controllers also may be used to transfer data between two locations in memory, or directly between I/O devices. The transfer of data by the DMA controller between some data source and to some data sink can be accomplished along a DMA channel.
A DMA channel is a path between the DMA controller and a device. The DMA channel typically passes data, command signals, and a clock signal to the device. However, transmitting a clock signal along an unused DMA channel can lead to unnecessary power consumption by the electronic device. Moreover, sending a clock signal along a DMA channel at a frequency higher than that required by the receiving device can also lead to unnecessary power consumption. This power consumption has become increasingly important as the demand for smaller portable electronic devices with long battery life and a wide range of functionality increases.